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Diff Question

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Racer 1966

Racer 1966

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It's been requested of me that I put on a show for the kids at my church again but my truck is broke! I blew the diff out yet again the last time out so I'm wanting to put in the bulletproof set from HPI. The problem is I can't afford to do both diffs at the same time plus the front diff is solid,haven't had an issue with it for years. So my question is this: Has anyone ran the bullet proof (29/9teeth) on one end and the stock set(43/13) on the other? Only a very slight gearing difference(3.31 vs 3.22) but one destroy the other?

Since at the church it will be part on the parking lot/part on the grass I'm thinking it could be an issue. I hate to pay for another stock set to blow up again but if I have to I will for the kids!
 
That is a really good question. I will look into this more and ask around, ill see if i can get an answer
 
I believe it will make a difference! You will have one overpowering the other and eventually breaking. It may last 5 mins or it may last 1hr. But it will eventually break. You need to run the same gearing in the front and rear my friend. Its easy to tell someone it is close enough not to matter when its not your money being spent to repair more damage.
 
Zdragon71 said:
I believe it will make a difference! You will have one overpowering the other and eventually breaking. It may last 5 mins or it may last 1hr. But it will eventually break. You need to run the same gearing in the front and rear my friend. Its easy to tell someone it is close enough not to matter when its not your money being spent to repair more damage.
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That's what I thought too. I know in a 1:1 they're unforgiving,just wish I could do both with bulletproof and be done. :\
 
hmmmm rear is getting more power now as it is always breaking. i'd take the front diff, put it to the rear...remove the front driveshaft and run it as a 2wd for your event. kids arent going to see its only 2wd and it will still haul the mail

anything good to trade? i have 2 new XSS differentials(29/9), housings and uprights i was gonna put into a 25 truck i have that has the plastic cups, but i dont really need to.already have 7 running trucks so i really dont have time for the 25 anyway
 
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This is a good idea^^^^. Plus you can just keep it 2wd until you can afford both front and rear bullet proof diffs. Just gonna be a bit squrilly on dirt being 2wd under full throttle but probably fun as all heck playing with it like so.
 
Lol yeh brakes only working on the rear suck. Setting up servo to act on the front and back individually would be the go.
 
bifft it said:
hmmmm rear is getting more power now as it is always breaking. i'd take the front diff, put it to the rear...remove the front driveshaft and run it as a 2wd for your event. kids arent going to see its only 2wd and it will still haul the mail

anything good to trade? i have 2 new XSS differentials(29/9), housings and uprights i was gonna put into a 25 truck i have that has the plastic cups, but i dont really need to.already have 7 running trucks so i really dont have time for the 25 anyway
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No,2wd is not a good idea. Done that before. Not only is braking an issue but you lose a lot of ability to control it during big jumps and back-flips.

I've got lots of r/c stuff,what kind of stuff you looking for?
 
.01 difference will not matter at all. The guy on "Extreme 4x4" did that with a full size blazer. I believe it was a 4:10 in back and 4:11 up front. Won't make a bit of difference, especially on an rc car.

On a 1:1 you can have more difference than that with just some worn tires on one axle :)
 
Yes, it would be possible on full size car especially on blazer but it has 2 types for the 4WD, there's All whell drive and there's switch or selector. And one thing very big difference on RPM nitro engines has more revolution than the ordinary car(full size).
 
I wouldn’t mismatch the diff ratios.
The actual difference in the ratio is 0.085:1 between the 2 diffs. Closer to .1 than .01

I have experimented with different diff ratios and different sized tire diameters.
With the same sized tires the .085:1 difference will put a large strain on the entire driveline and something will wear out/break quickly.

An easy way to see just what the difference will do is to install the diffs and then let the truck roll down a hill. You will see very quickly it is not a good idea.
 
Obviously you should match the ratios, but if you're in a pinch, run it! That is such a small ratio it could literally be the difference of slightly worn tires on one axle and new tires on the other.
 
Yes i do run a truck with the old ratio in the rear and new in the front so i do speak from experience. You have none so think before you call somebody out Zlizzard

It wont matter. There is enough slack/slop in the tranny to negate any difference. When these diffs first appeared, many people had the same question. Theres a post on savage central with an email from hpi saying it wont matter.

If the drive train was that tight so that small of an increment would make a difference you would bust your drive line every time you wheelied or jumped etc.
 
On a drive train there is always some room for play, these cars/trucks are like like there big brother counterparts, in a ideal world yes the same ratios are what you would want for best performance, however it's not ideal, two ratios work but they have to be close together, if you skip a ratio you will have binding in the drivetrain,

I run a pull truck ( tractor pulling fun machine) that runs two different gear sets and from experience you want the lower ( numerical higher) in the back and the higher ratio in the front,

the front end you always want to spin faster because when you speed up the weight transfer will move to the rear of the vehicle which makes the front lighter, there is also the reason of having the front tires clean the path for the rears when your out running. Gets more technical and I can explain this at a later date.




Sent from my smartass phone
 
There will be some preload on the driveline, Snook is right about that. As for actual slack, you'd want as little as possible, but slack isn't really a factor here. The preload would contribute to premature wear, but I doubt you'd ever notice it.
All I really wanted to say is I wouldn't let it stop me from putting on a show for the kids.:D

Canadian diesel is right too, I'd have it so the fronts were kind of dragging the rears along.
 

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